1. Field of the Invention
The present invention relates to the field of internal combustion engines such as diesel engines, gasoline engines and engines designed to operate on other or alternate fuels.
2. Prior Art
The preferred embodiments of the present invention are intended to be used in engines of the general type disclosed in U.S. Published Application No. 2007/0245982, published on Oct. 25, 2007, the disclosure of which is hereby incorporated by reference. That application discloses engines that compress air in a compression cylinder and inject fuel or fuel and air into a combustion cylinder during a compression stroke, and air or fuel and air after ignition. Of particular interest to the present invention is the method of operating an engine disclosed therein of injecting fuel or fuel and a little air into the residual hot exhaust gases during the compression stroke to convert the fuel to a gaseous form, then obtaining compression ignition, typically at or near top dead center, using the oxygen in the residual exhaust gases and air injected, if any, and then injecting air after the piston in the combustion cylinder moves past top dead center to maintain combustion during the power stroke. Such a method of operation better mixes the fuel and air, helps avoid local hot spots in the combustion cylinder, and allows an overall control of combustion for more complete combustion and to avoid combustion temperatures at which NOX will be formed. It also extends combustion through a greater crankshaft angle for more efficient energy conversion to engine shaft output power. Still, in comparison to conventional diesel engines wherein fuel is injected into an oxygen rich environment, the above described method injects air into a fuel rich environment, either of which has the potential to cause NOX or soot formation.
Also the embodiments in the foregoing disclosure contemplated use of a high pressure storage tank for storing air for injection, and could also store compressed air when the engine was being used as a brake to recover some of that energy for later use. While storing compressed air when the engine is being used as a brake to recover some of that energy for later use is practical, pumping air into and injecting air from a storage tank in normal engine operation is less than ideal, in that considerable energy can be lost by the intervening cooling of the compressed air.
The engines of U.S. Published Application No. 2007/0245982 use camless engines of the general type disclosed in U.S. Pat. No. 6,739,293, the disclosure of which is hereby incorporated herein by reference.